President Donald Trump announced in March the United States would slap a 25 percent tariff on imported steel, and a 10 percent tariff on imported aluminum.

President Donald Trump's administration is planning to impose tariffs on European steel and aluminum imports after failing to win concessions from the European Union, a move that could provoke retaliatory tariffs and inflame trans-Atlantic trade tensions.

The tariffs are likely to go into effect on the EU with an announcement by Friday's deadline, according to two people familiar with the discussions. The administration's plans could change if the two sides are able to reach a last-minute agreement, said the people, who spoke on condition of anonymity to discuss internal deliberations.

Trump announced in March the United States would slap a 25 percent tariff on imported steel, and a 10 percent tariff on imported aluminum, citing national security interests. But he granted an exemption to the EU and other U.S. allies; that reprieve expires Friday.

Europe has been bracing for the U.S. to place the restrictions even as top European officials have held last-ditch talks in Paris with American trade officials to try to avert the tariffs.

"Realistically, I do not think we can hope" to avoid either U.S. tariffs or quotas on steel and aluminum, said Cecilia Malmstrom, the European Union's trade commissioner. Even if the U.S. were to agree to waive the tariffs on imported steel and aluminum, Malmstrom said, "I expect them nonetheless to want to impose some sort of cap on EU exports."

European officials said they expected the U.S. to announce its final decision Thursday.

U.S. Commerce Secretary Wilbur Ross attended meetings at the Organization for Economic Cooperation and Development in Paris on Wednesday, and U.S. Trade Representative Robert Lighthizer joins discussions in Paris on Thursday.

Metal coils are seen at ArcelorMittal steel plant in Ghent, Belgium, May 22, 2018.REUTERS/Yves Herman

The U.S. plan has raised the threat of retaliation from Europe and fears of a global trade war — a prospect that is already weighing on investor confidence and could hinder the global economic upturn.

If the U.S. moves forward with its tariffs, the EU has threatened to impose retaliatory tariffs on U.S. orange juice, peanut butter and other goods in return. French Finance Minister Bruno Le Maire pledged that the European response would be "united and firm."

Besides the U.S. steel and aluminum tariffs, the Trump administration is also investigating possible limits on foreign cars in the name of national security.

"Unilateral responses and threats over trade war will solve nothing of the serious imbalances in the world trade. Nothing," French President Emmanuel Macron said in an impassioned speech at the Organization for Economic Cooperation and Development in Paris.

In a clear reference to Trump, Macron added: "These solutions might bring symbolic satisfaction in the short term. ... One can think about making voters happy by saying, 'I have a victory, I'll change the rules, you'll see.'"

But Macron said those "who waged bilateral trade wars ... saw an increase in prices and an increase in unemployment."

Tariffs on steel imports to the U.S. can help local producers of the metal by making foreign products more expensive. But they can also increase costs more broadly for U.S. manufacturers who cannot source all their steel locally and need to import the raw material. That hurts the companies and can lead to more expensive consumer prices, economists say.

Ross criticized the EU for its tough negotiating position.

"There can be negotiations with or without tariffs in place. There are plenty of tariffs the EU has on us. It's not that we can't talk just because there's tariffs," he said. He noted that "China has not used that as an excuse not to negotiate."

U.S. Commerce Secretary Wilbur Ross arrives at a Senate Commerce, Justice, Science and Related Agencies Subcommittee holds a hearing on the FY2019 funding request and budget justification for the Commerce Department on Capitol Hill in Washington, D.C., May 10, 2018.REUTERS/Yuri Gripas

But German Economy Minister Peter Altmaier insisted the Europeans were being "constructive" and were ready to negotiate special trade arrangements, notably for liquefied natural gas and industrial goods, including cars.

Macron also proposed to start negotiations between the U.S., the EU, China and Japan to reshape the World Trade Organization to better regulate trade. Discussions could then be expanded to include other countries to agree on changes by the end of the year.

Ross expressed concern that the Geneva-based World Trade Organization and other organizations are too rigid and slow to adapt to changes in global business.

"We would operate within (multilateral) frameworks if we were convinced that people would move quickly," he said.

Ross and Lighthizer seemed like the odd men out at this week's gathering at the OECD, an international economic agency that includes the U.S. as a prominent member.

The agency issued a report Wednesday saying "the threat of trade restrictions has begun to adversely affect confidence" and tariffs "would negatively influence investment and jobs."